Pressure rollers are resilient rollers that serve to create a pressure in a nip. Nip pressure and control are of critical importance in processes such as embossing and laminating, as well as for web control and draw. Pressure is applied to a pressure roller at the outer ends of the roller. The resilience of the roller material creates a loading on the central shaft or core of the roller that is similar to pressure profiles found in structural beam loading. This causes the central core to bend under a load so that the surface of contact and pressure in the nip is not uniform along the nip. To compensate for this undesirable condition, it is common practice to crown the center portion of the roller. This practice results in uneven wear due to differences in hysteresis in different areas of the roller as well as uneven areas of contact of the roller surface as well as uneven nip bulge and other undesirable operating characteristics.
Wearing of the surface is an important determiner of roller life and usefulness. It is common practice to provide rollers with an outer coating or sleeve that is wear resistant. The coatings or sleeves are typically adhered or shrunk into place.